Method of disposing of sewage sludge



Jan. 24, J, E, GREENAWALT 1,895,159

METHOD OF DISPOSING OF SEWAGE SLUDGE Filed July 31, 1931 H TO NEK.

Patented Jan. 24, 1933 aonitn GREENAWALT, or NEWY RK, 'N. Y,

fin'i fion oi nrsrosmo or siw AGE stapes Application medial? 31, 1931. Serial m. sagas.

My invention has relation tojimprovcnient's in methods of disposing oi sewage sludge and it consists in the novel manner of treating the same more fully set forth in "the specification and pointed outin the claims. The invention is disposalplants and it consists in a heat treatment, whereby the sludge as such, completely destroyed and a new and useful product produced. The principal object of the invention is, of course,an economical disposal of the sludge, and a further object of the invention is to obtain from the process-a useful product having entirely different prop erties than the mixture of material from which it was made. 7 p 7 r The practice now largely adhered to at sewage disposal plants is to treat the sewage with certain chemicals Which 'killthe' bacteria and eliminate ofiens ive odors and, at thesame time, facilitate the settling oi the solids This precipitate suspended in the solution;

is thesludge that I propose to dispose of m'y improved process.

Since the sludge siderable water, it is not easily disposed of by burning a's'itmust be dried," and it is. not particularly valuable as fertilizer-.1 The sludge issoinetimes formed into a cake by removing a large amount of the Water by vacuum filtration, but the disposal of this material is also unsatisfactory, as the cost is excessive compared to the value of the tertiliz'er obtained.

My improved method of disposing of the sludge comprises burning it by a sintering operation. As is Well known in the metal lurgical industry, sintering contemplates the burning of a substance formed in' a' layer on a pervious hearth, or other support, the burning being dependent Y on fuel distributed throughout the mass'of the substanceand ablast of air continually passedthrou'gh'the mass until combustion iscomplete.

Obviously, the physical condition of the sludge, the sintering of which I am about to describe, is such that it could not be main-- tained on a pervious support, nor could air be passed through it, unless it is first properly particularly. directed to the disposal of sludge obtained' from sewage charge;

is combined t'vith con I waste, product, 111 ;a. fine1y divided cenditio'm- Obviously, the charge "may i be modified, m

prepared by the admixtureofbther substances. inventioncontemplates the mixing of s'lud gefwith a Water absoi'ptive material in a loose condition, such as" ashes,

so that the pastiness'of the-,sludgemay be, counteracted and enable the mass to be dis-1 posed in "a porouslayer. I-h'ave found by experience that of sludge and 50% ot'-- ashes willproduce a mixture that will fenn- 'a,'fs'ati'si'actory' charge. The' ashes produce a sufficient volumelof voids in the charge to permit the passage of therethrough, and the moisture gives the body of the chargeth-e necessary firmness togenable'it to Withstand the blast of'air applied for the purpose "of supporting the "combustion of the fuel i-I'ithe v The fuel content of the charge is provided by the ashes as therei s always some coke. Of course, if i't should be found byn-ial that the ashes use-ct do not contain ci'ent fuel c'o'ntent'to support combustion, it. is a simple matter to add a small percentage 1 'fuel present in ashes-intheiorm of coal, v v

of "fuel in the Shape of finely divided coal-or V. .7

' carbon. In fact, additional fuel :be

added, as sawdust, or other combustible that clay, or some other earthy substance may be substituted for the ashes, v'vhich event additional fuel must be addedpreferably of a. bulky material, such as sawdust, or perhaps shavings. It shouldbe oorne inmind that which will barman thecourseofthe Sinteliiig operation and augment the fuel contentof the charge. However, to depend on the combustible p'roperty'of the sludge alone for maintaining combustion is not practical, since the sludge-is notag easily kindledas the fuel" imported with ingredient; a I v After the sludge has been embodied into-a the ashes, or as se arate action will be more .easily understood sintering charge as above explained, this sludge charge is arranged on a grate, or pervious support and ignited at its surface. Ignition is facilitated by the drafting of a blast of air downwardly through the charge, which also propagates the combustion of the'fuel throughout the charge. The combustion proceeds downwardly through the charge substantial-ly' simultaneously throughout the extent of the charge, leaving behind a sinter, or. porous agglomerate. This sintering by referring to'the drawin in'whicli a"Greenawalt sintering apparatus is shown more or less conventionally. 7

v In the; drawing, -1 represents a sintering pan, or holder l'lLVlIlgfi grate2 for the support of the charge C. The charge 0 is light- 'ly depositedand evenly distributed on the grate 2 ,by a charge car 3 designed for the "purpose. Thischargecar may have two com- I part-ments a, and a, one, .of'which would.

hold the more finely divided component in of the materialto be treated, and the other the coarser component m. of the material.

In arranging the charge on the gratev the coarser component of the material m will be first deposited, and the more finely divided component m will be deposited on the coarser component. This method" of arranging the; charge insures a more even combusiuon and results in a product of substantially uniform eration, a blast of air will be sucked-downwardly through the charge' (The charge is r kindled.- at its surface by means of an ignition? F hood 7 which is removedjust as soon as ignition is accomplished and combustion proceeds through the charge'under the influence- ,of the air blast. The air blast is continued density; Of course, it is not obligatory to arrange the .charge in ,two' components, as

very'satisfactory results are obtained when the charge car has but a'single materialhopper andthe material is fed into the pan as a single layer. s 1 v A fan tis connected by means of conduits the'pan, and on; putting the fan 4 into opuntil the. charge has been completely sintered from top to bottom, a'fte'r which the panmay be rotated on its trunnionsand the resulting sintered product dumped. This sintered product is in the shape of a hard cellular cake, or porous agglomerate, and is suitable for, useas an aggregate forconcrete or any ,kindred purpose. Obviously, the. physical" properties of the sintered mass may be varied by varying the composition of the charge with respect to the addition of an inert sub-f stance and, controlling .thejamount of fuel, 1 so tha't a'product having a wide range of properties anduses'ma'y be obtained.

"er'towardthe opposite surface to causeconr, l 100:

. commingling sewage slud "therethrcugh.

face to cause combustion to out the mass thereof.

commingling sewage sludge with finely di videdmaterial capable of absorbing moisture,

disposing said mixture as a layer on'a previous support,ignit1ng' thelayer at one surface,

and forcing air through'saidlayer toward the opposite surface to cause combustion to proceed through the layer.

2. The process of manufacturing a con air through the layer toward the opposite surface s to cause combustion to proceed through the layer, I g, f 8. The process of manufacturing a concrete aggregate which comprises thoroughly commingling sewage sludge with ashes, or similar material, in a finely divided state, ar rangingsaid mixture as a layer on a pervious 1 support, igniting the layer at one surface and forcing air through-said layer toward the opposite surface to cause combustion to proceedthrough the layer." I u 4. The process ofmanufacturinga concrete aggregate-which comprises thoroughly commingling sewage sludge with a substantially equal quantity of vashes in a finely divided state,arranging said' mixture as a layer on a pervious support, igniting. thelayer at one surface and forcing air through said laybustion to proceed through the layer.

5. The process of manufacturingaiconcrete aggregate which comprises thoroughly vided material capable of absorbingucie. ture, disposing said mixture as alayer ona pervious support, igniting said. layer at the: top and forcing air downwardly through. the layer to cause combustion to proceed 6;. The process of manufacturing aconcrete aggi egate which comprises thoroughly" commingling sewage sludge with ashesina I finely divided state, separatingsaid mixture into two components ticles, arranging the component of coarser particles ina layer on Y I disposing the component of finer particles on said layer, igniting the charge .thus" formed at one surface and forcing air through the charge toward the opposite surproceed .throughge with finely diaccording to size of par- 1 "In testimony whereof I hereunto aifiii signature.

JOH -E. GREENAWALT.

Having'described my invention, I 'claimr V 1 The process of manufacturinga con-g P a re wh h" omp i es roug y the pervioussupport, a 

